The invention relates to a apparatus for reading a line marking fixed to a carrier, the marking having longitudinal elements of different lengths which are substantially perpendicular to a joint, imaginary line, shorter elements being for use as pulse generator markings and longer elements being for use both as pulse generator markings and code symbols. The elements are not necessarily continuous as they may comprise several dots. The apparatus operates with an optical arrangement which displays the elements in time sequence on a reading surface in the movement of the marking carrier in the direction of the imaginary line.
Line markings of various types and apparatuses for reading such markings are customarily used for different applications and in different forms. A first known version, in which the markings are printed on the flat surface of a packaging container, is disclosed and described for instance in U.S. Pat. No. 3,651,465 (Law et al). Another known version, in which the markings are affixed in relief on the curved wall of a container, is described for instance in Swiss Pat. No. 607161 (Emhart) which corresponds to U.S. Pat. No. 4,201,338 and German Pat. No. 27 26 162.
The apparatuses for reading the markings which were disclosed in the said publications have two optoelectronic converters, of which one is linked to the pulse generator markings and the other to the code symbols. To ensure that the markings and symbols act only on the appropriate converter, the entire marking needs to be moved across the reading range of the device and along a specific path, and the individual elements of the marking must not be off-set in their longitudinal direction or be outside the specific range.
These conditions are relatively easily fulfilled in the case of the first markings mentioned in that the markings and the symbols are relatively long and the distance between the optoelectronic converters in the reading device is relatively large.
In the case of the second version mentioned, these conditions are however difficult to fulfil. The reasons for this lie both with the container and its manufacture and with the guide mechanism forming part of the reading device.
The length of the elements is restricted because the markings are preferably fixed on the base inlet of the container wall so as not to protrude above the side wall. Furthermore, each marking to be affixed must be individually engraved on a mould, so that relatively large tolerances with regard to the length of the line marking and the mutual alignment of the lines are inevitable. Finally, the moulds are subject to gradual deformation during use and the hot-formed containers sag during the cooling process, both of which can lead to deformations in the markings.
The support surface of the guide mechanism, in which a container is rotated so that the marking can be read, is exposed to continuous wear and tear which will alter the position of the containers in the guide mechanism and, thus, the position of the markings in the reading range. Furthermore, the high speeds used to transport the glass containers through the reading device make it inevitable that a container is raised when being rotated in the retention rollers which will also result in a displacement of the markings outside the reading range. Finally, it is also possible that a container is not rotated around the correct axis or that it is not properly round, so that the markings will not be accurately displayed by the optical system on the optoelectronic converters.
Due to the possible defects shown in both the markings and the guide mechanism, known reading apparatuses cannot read the markings fixed to containers with the required accuracy in the short time available.
The invention therefore has the object of providing an apparatus for reading line markings fixed to a carrier which allows the individual elements of the marking to be read in an accurate manner, even if these elements are of a relatively short length and are off-set in their longitudinal direction as a group or relative to one another.